1. Technical Field
The invention relates to a semiconductor device and an oscillator. More specifically, the invention relates the semiconductor device in which a resin layer is formed on a semiconductor substrate including an integrated circuit and further in which passive elements composed of Cu wiring layers are formed on a surface of the resin layer, and the oscillator formed in the semiconductor device by the passive elements.
2. Related Art
According to the related art example, a voltage controlled oscillator formed in the semiconductor device having the semiconductor substrate and a multi-layered wiring layer mounted thereon in which output terminals, spiral inductors which are provided on the multi-layered wiring layer and connected to the output terminals, variable capacitors which are formed on an area where an area immediately below the spiral inductors is included but a central axis of the spiral inductors is not included and which are connected to the spiral inductors in parallel to form a resonance circuit together with the spiral inductors has been known. JP-A-2005-6153 at page 5 and in FIGS. 1 and 2 is the example of the above described related art.
As described in the example, the spiral inductors formed on the surface of the multi-layered wiring layer on the semiconductor substrate and variable capacitors provided in the integrated circuit which is composed of the semiconductor substrate and the multi-layered wiring layer constitute the resonant circuit. Because such spiral inductors are generally formed of Al wiring, there involves a problem that a phase noise characteristic can not be improved since, for example, a specific resistance of Al wiring is larger than that of the Cu wiring by approximately 30% and Q values of the inductors are low.
The above stated variable capacitors are formed in the integrated circuit of the semiconductor substrate, such that there are restrictions in capacity of capacitance and sizes of opposite electrodes due to the existing limitations in applicable dielectric material for forming the capacitors and sizes of opposite electrodes. Therefore, it is not possible to realize to manufacture the oscillator having a low frequency area, or to broaden a selectable width of the frequency.